The present invention pertains to systems for rotatably driving aircraft wheels for taxiing or other ground handling operations of an aircraft.
With the increasing size of aircraft, there is a need for powering aircraft wheels, so that the airplane can be self-propelled in an easily controlled ground drive mode without using the main aircraft propulsion engines for thrust. However, the technical problems encountered in providing such an auxiliary drive system for aircraft wheels are numerous. For example, the wheel drive system must not add excessive weight to the aircraft; it must not be so complex that it is unreliable and difficult to service; it must generate sufficient power and efficiently deliver such power to the wheels in order to propel hugh aircraft transports; provision must be made for disconnecting or decoupling the drive from the aircraft wheels for normal taxi, take-off and landing; and typically provision must be made for reduction gearing between the auxiliary wheel drive motors and the wheels.
Previous attempts have been made to provide an auxiliary motor drive for aircraft wheel assemblies, such as disclosed in U.S. Pat. No. 3,711,043 issued on Jan. 16, 1973 to Alan Cameron-Johnson. However, none of these prior art efforts have been found satisfactory. For example, in the above-mentioned U.S. Pat. No. 3,711,043, separate clutch and wheel brake assemblies are utilized for coupling the auxiliary motor to the wheel and braking the wheel respectively, resulting in a relatively complex, mechanism and one which is subject to malfunction because of the substantial torque load which must be handled by the separate clutch for the auxiliary motor drive. Additionally, by utilizing a separate, independent clutch assembly for coupling the wheel drive motor to the wheel itself, it is generally necessary to mount the clutch assembly, and in some cases the drive motor in close proximity to the aircraft wheel assembly, resulting in a cramped system which limits the design flexibility of the components and makes servicing of the assemblies difficult.